To obtain a high-definition image, reduction in bending or vibration of a table top in a bore is required. For this purpose, a bed apparatus, in which a support frame supporting the table top can approach to a gantry, has been developed. For example, in a known system, the table top and the support frame move forward and backward while moving up and down. If this system is adopted, when the table top and the support frame are moved up, they inevitably protrude. To avoid this protrusion during positioning of the table top and the support frame in a bore, the position in a forward-backward direction of the table top and the support frame is corrected based on the position in an up-down direction thereof. However, this system cannot correct the position accurately, because movement information on directions other than the forward-backward direction, for example, the up-down direction, need to be converted to a position in the forward-backward direction.